A381032 The radix prime of the least significant digit > 1 in the primorial base expansion of n, or 1 if there is no such digit.

1, 1, 1, 1, 3, 3, 1, 1, 1, 1, 3, 3, 5, 5, 5, 5, 3, 3, 5, 5, 5, 5, 3, 3, 5, 5, 5, 5, 3, 3, 1, 1, 1, 1, 3, 3, 1, 1, 1, 1, 3, 3, 5, 5, 5, 5, 3, 3, 5, 5, 5, 5, 3, 3, 5, 5, 5, 5, 3, 3, 7, 7, 7, 7, 3, 3, 7, 7, 7, 7, 3, 3, 5, 5, 5, 5, 3, 3, 5, 5, 5, 5, 3, 3, 5, 5, 5, 5, 3, 3, 7, 7, 7, 7, 3, 3, 7, 7, 7, 7, 3, 3, 5, 5, 5, 5, 3, 3, 5

Offset: 0

Author

Antti Karttunen, Feb 13 2025

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 0..65537
• Index entries for sequences related to primorial base.

Crossrefs

Cf. A008578, A020639, A249739, A276086, A327860, A328572, A328828, A381033, A381034.

Cf. A088860 (positions of records for values > 1), A276156 (positions of 1's).

Cf. also A053669, A351566.

Programs

PARI

A381032(n) = { my(p=2); while(n, if((n%p)>1, return(p)); n = n\p; p = nextprime(1+p)); (1); };

Formula

a(n) = A008578(1+A328828(n)).

a(n) = A020639(A328572(n)) = A249739(A276086(n)).

For all n, a(n) divides A327860(n).